In patients suffering with a lack of a renal function or a liver function, harmful toxic substances are accumulated or formed in bodies, such as blood, with a progress of a disorder of the organ functions, and thus an encephalopathia occurs, such as a disturbance of consciousness or uremia. Yearly, there is a growing number of such patients, and therefore, the development of an organ-substitute apparatus or medicament having a function to remove toxic substances from bodies, in place of such defective organs, has become a serious problem. A method for removing toxic substances by hemodialysis as an artificial kidney is prevalent. Nevertheless, the hemodialysis-based artificial kidney requires a special apparatus, and thus, a skilled specialist is required from a safe operation standpoint. Further, blood must be taken from a patient's body, and thus, there are disadvantages in that patients must bear high physical, mental and economic burdens. Accordingly, hemodialysis is not satisfactory.
Recently, as a means of remedying the above disadvantages, an oral adsorbent which can be orally administered and cure a disorder of renal and liver functions has received considerable attention. Specifically, an adsorbent disclosed in Japanese Examined Patent Publication (Kokoku) No. 62-11611 comprises a porous spherical carbonaceous substance having particular functional groups (hereinafter referred to as a surface-modified spherical activated carbon); having a high safety factor and stable to a body; and having a useful selective adsorbability, that is, an excellent adsorbability of harmful substances in the presence of a bile acid in an intestine, and a low adsorbability of useful substances such as digestive enzymes in the intestine. For these reasons, the oral adsorbent is widely and clinically used for a patient suffering from a disorder of a liver or renal function, as an adsorbent having few side effects such as constipation. The above adsorbent disclosed in Japanese Examined Patent Publication (Kokoku) No. 62-11611 was prepared by forming a spherical activated carbon from a pitch such as a petroleum pitch as a carbon source, and then carrying out an oxidizing treatment and a reducing treatment.